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Renzulli, Alberto
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- PublicationOpen AccessSoil CO2 flux and temperature from a new geothermal area in the Cordón de Inacaliri Volcanic Complex (northern Chile)This paper deals with the first geochemical data from an unexplored sector of the Cordón de Inacaliri Volcanic Complex (Central Andes, Chile). The site is located at ∼5,150-5,200 m a.s.l., inside the Pabelloncito graben where, at about 9 km NW of the studied area, the only currently working geothermal power plant of South America, named Cerro Pabellón, occurs. Diffuse soil CO2 and soil temperature measurements were carried out to unravel the structural control on the rising fluids and estimate the total CO2 output, the heat flow rate and the heat flux, aimed at assessing a preliminary evaluation of the geothermal potential of the area. The study area is characterized by a pervasive hydrothermal mineralogical alteration, CO2 flux values of up to ∼4,400 g m-2 d-1 and soil temperatures up to the boiling point of water at that altitude. All these features are likely related to an endogenous source. Spatial distribution of both soil CO2 flux and temperature depict an ENE-striking lineament, whose intersection with the NW-striking Pabelloncito graben forms a favourable structural setting for the discharge of hydrothermal fluids. The total CO2 output emission of the studied area (∼0.0179 km2) was ∼0.53 t d-1, with an associated discharge of steam of 6.45 t d-1 (CO2/H2O ratio = 0.08). An electric capacity potential of 1.08 MWe km-2 was computed from the heat flow rate and heat flux values. Our results suggest that this part of the Pabelloncito graben is an interesting geothermal prospect and a good candidate for further exploration studies.
28 62 - PublicationRestrictedCarbon isotope composition of CO2-rich inclusions in cumulate-forming mantle minerals from Stromboli volcano (Italy)(2017-04-04)
; ; ; ; ; ; ; ; ;We report on measurements of concentration and carbon isotope composition (δ13CCO2) of CO2 trapped in fluid inclusions of olivine and clinopyroxene crystals separated from San Bartolo ultramafic cumulate Xenoliths (SBX) formed at mantle depth (i.e., beneath a shallow Moho supposed to be at 14.8 km). These cumulates, erupted about 2 ka ago at Stromboli volcano (Italy), have been already investigated by Martelli et al. (2014) mainly for Sr-Nd isotopes and for their noble gases geochemistry. The concentration of CO2 varies of one order of magnitude from 3.8·10−8 mol g−1 to 4.8·10−7 mol g−1, with δ13C values between −2.8‰ and −1.5‰ vs V-PDB. These values overlap the range of measurements performed in the crater gases emitted at Stromboli (−2.5‰ b δ13CCO2 b −1.0‰). Since SBX formed from relatively primitive mantle-derived basic magmas, we argue that the isotope composition displayed by fluid inclusions and surface gases can be considered representative of the magma volatile imprinting released by partial melting of the mantle source beneath Stromboli (−2.8‰ b δ13C b−1.0‰). In addition, the δ13C signature of CO2 is not significantly modified by fractionation due to magmatic degassing or intracrustal contamination processes owing tomagma ascent and residence within the volcano plumbing system. Such δ13C values are higher than those commonly reported for MORB-like upper mantle (−8÷−4‰) and likely reflect the source contamination of the localmantlewedge by CO2 coming from the decarbonation of the sediments carried by the subducting Ionian slabwith a contribution of organic carbon up to 7%.247 6 - PublicationEmbargoAge of the Valle del Bove formation and chronology of the post-collapse flank eruptions, Etna volcano (Italy)(2023)
; ; ; ; ; ; ; ; ; ; ; The Valle del Bove is a profound and wide scar on the east Etna flank witnessing the Holocene main volcanotectonic event of the volcano, frequently invaded by lava flows during the last centuries. The Valle del Bove slope failure produced the Milo debris avalanche deposit on the lower east flank that is partially covered by the Mongibello lavas and a pyroclastic succession. In this paper, we constrain for the first time the age of the Milo debris avalanche deposit and the overlying lava succession exposed at three quarries recently caved at the valley mouth through a multidisciplinary approach integrating stratigraphic and petrographic analyses, 14C, and paleomagnetic dating. In particular, 14C age determinations of the Milo debris avalanche deposit indicate that the initial stage of the catastrophic flank collapse of the Valle del Bove occurred at 7478–7134 BCE during the Mesolithic age. Conversely, the main portion of the lava succession filling the valley floor emplaced after the sub- Plinian picritic eruption occurred at 2579–2278 BCE (FS tephra layer) consistently with the increasing occurrence frequency of flank eruptions documented in the geological record of Etna during the past 4000 yrs. Paleomagnetic dating highlighted that in the study area the sub-Plinian eruption was followed by two quasicontemporaneous flank eruptions during the Late Copper age (2600–2400 BCE), whereas other two flank eruptions occurred during Greek-Roman and Medieval ages. These results have relevant implications on the stratigraphy and evolution of Etna, particularly on the Valle del Bove initial collapse and the relative emplacement of the Chiancone detritic-alluvial sequence.866 2 - PublicationOpen AccessVolcanic Grinding Tools in Ustica Island (Tyrrhenian Sea, Italy): Local Production vs. Import of Morgantina-Type Millstones in the Hellenistic-Roman Period(2020-04)
; ; ; ; ; ; ; ; ; This archaeometric study was focused on 28 grey to dark-grey lava artifacts found in Ustica Island (Southern Tyrrhenian Sea, Italy) and referable to different grinding tools: saddle querns, rotary Morgantina-type millstones, rotary hand-mills and one small mortar. Mineralogy, petrography and bulk rock geochemical analyses emphasized that most of the grinding artifacts belonged to the Na-Alkaline series of Ustica, mainly basalts, hawaiites and mugearites. Nevertheless, some millstone samples did not match major and trace elements of Ustica lavas, in particular, one high-TiO2 Na-Alkaline basalt from Pantelleria Island, some tholeiitic/transitional basalts from the Iblei Mountains and one Calcalkaline basaltic andesite, most likely from the Aeolian Archipelago. The Hellenistic–Roman re-colonisation of Ustica Island, after ca. one millennium of nearly complete abandonment, was testified by the import of the non-local Morgantina-type rotary millstones, very widespread in the Mediterranean area from 4th–3rd century BC. This import of millstones represented, for the Ustica inhabitants, a real breakthrough for developing a local production of grinding artifacts on the basis of the new rotary technique which was much more efficient than that of the archaic saddle querns, largely used in the Middle Bronze Age. The results are also discussed in the framework of the overall volcanic millstone trade in the Mediterranean area and the different milling technology in antiquity.268 87